MB-1143: initial server groups UI

Change-Id: Ifa3984c24f08720877139666656866642ab9b217
Reviewed-on: http://review.couchbase.org/29661
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>